Dan D’Agostino Relentless 800 Monaural Amplifier

Description

Relentless 800: Performance in a smaller package

After setting the measure for amplifier excellence, the new Relentless 800 Mono Amplifier extends the Relentless sound quality to a smaller platform.

Every major section of the Relentless circuitry – power supply, input, driver, and output stages – have all been enhanced and these all feature in the new Relentless 800. The Relentless 800 incorporates the same circuit platform as its bigger brother with a lower power output. Mind you, the Relentless 800 is virtually unlimited when it comes to power delivery and is only outdone by the Relentless 1600 itself. Nuanced and musical at low volume levels, the Relentless 800 delivers the striking dynamic contrasts – that brings music to life.

Power to Spare

The core of the Relentless Amplifiers’ power supply is a transformer that uses multiple sections running in concert, all potted and encased in a metal shield. This design reduces transformer noise to near zero and protects the audio circuitry from the transformer’s magnetic field. A special holder mechanically grounds each capacitor eliminating vibrations.

With its nearly four-kilowatt transformer and 400,000 F capacitance power supply feeding 84 output devices, the Relentless 800 easily delivers 800 watts into 8 ohms—and when connected to a 220-volt outlet, doubles its output to 1,600 watts into 4 ohms and 3,200 watts into 2 ohms.

The Design

The Relentless 800 employs an all-new, fully complementary design based around a precision input stage that maintains an essentially perfect balance between the positive and negative components of the signal. Any distortion artifacts that appear on one half of the signal will also appear on the other half, and thus cancel each other. Gain circuits operate in the current domain, assuring the amplifiers’ performance does not fluctuate regardless of the speaker demand. In the Relentless 800 amplifiers, new input stage devices deliver a 300% increase in current as compared to the previous devices. These wider bandwidth, higher power components extend low and high frequency performance with reduced distortion in both frequency extremes. Global negative feedback is not employed, nor is it required as the amplifiers’ open-loop linearity eliminates the need for this performance-robbing technique.

Activating the reimagined driver stage is a new bias stability circuit providing a nearly 50% increase in operating bias. Increasing Class A operation directly correlates to better sound quality. With this new circuit topology and the unique Copper/Aluminum heatsinks, thermal issues are irrelevant in the Relentless 800 amplifier. The new scheme ensures bias consistency, preventing excessive temperatures even under the greatest demand.

A critical element of any amplifier output topology is the driver section. In the new Relentless 800 amplifiers, the driver transistor has been upgraded to a new device that handles 33% more power per device. Additionally, the driver transistor count has doubled thus minimizing demand on each individual device and lowering overall amplifier output impedance without resorting to global negative feedback. Individual transistors are used for the positive and negative signal elements in an inter-digitated complementary arrangement. This nearly doubles the current drive necessary to maximize the enhanced output stage that follows.

Super Rails

Super Rail employs higher voltage rails in the sections prior to the output stage, effectively “turbocharging” the amplifier and exploiting the full capability of the output voltage rails—which improves dynamics, lowers distortion, and tightens the amplifiers’ electrical grip on the speaker.

The output stage features the same new transistor as in the driver section for sonic and technical consistency. Individual complementary pairs undergo our transistor matching protocol to ensure that gain linearity is virtually identical from 50mA to 5A. Additionally, every one of the 84 output transistors used is measured and only devices that match the required performance specifications are included in the production of Relentless 800 amplifiers. The high-output transistors used in the Relentless 800 are among the fastest available. These high-powered transistors mount with two stainless steel fasteners—a rarity among flat-package transistors—for maximum thermal transfer to the copper heat sinks. A capacitor/resistor network connected to the base of each transistor guarantees stability even at high frequencies and with low-impedance speakers. As with all D’Agostino models, the Relentless 800 amplifiers feature discrete, direct-coupled balanced circuitry – the most accurate circuit platform possible.

Elegantly Functional

The Relentless 800 Amplifier’s unique heat sink combines copper and aluminum in a thermal engine that wicks away heat from the connected devices. The elaborate elliptical design expands on the venturi heat sink first explored in the Momentum series and makes certain that the Relentless amplifiers run safely and reliably even when delivering its full rated power. Thermal, short circuit, and DC protection are included in a non-invasive but comprehensive defense against any external system faults.

The entire chassis of the Relentless 800 amplifiers are machined from solid aluminum, for superior shielding, thermal stability, and vibration damping. High-precision milling allows the entire chassis to fit together solidly with no visible fasteners.

Awards

“It acquired what I can only describe as ‘Humanity.'”
-Ken Kessler